Zener diode, voltage divider, or other?

Discussion in 'General Electronics Chat' started by mrjimbo, Aug 3, 2011.

  1. mrjimbo

    Thread Starter New Member

    Aug 3, 2011
    With a portion of my circuit, and I trying to accomplish two things:

    1) Quickly charge two series capacitors (200mF each) with 10V to later discharge with about 4 amps of current by the 15ms mark.

    2) Tap off of this holding-charge to activate a solid state relay (PVN012A) that will connect two 3V coin cell batteries to the AVR microcontroller. Basically, this is acting as a power switch to the microcontroller. So, when the caps are not charged, then the microcontroller isn't wasting battery power.

    What component/method should I use to accomplish the above steps without:

    a) hindering the charge-up time too much on the caps, and
    b) pushing an excessive surge of current/voltage to the solid state relay (inside is basically an LED, max biasing current is 25mA, max reverse voltage is 6VDC, made by International Rectifier)?

    I guess my basic question is, should I use a zener diode or a resistor voltage divider to provide the sufficient voltage/current to the solid state relay without messing up my charging time of the capacitors?

    As it stands now, I am able to charge up the caps within 2-3 secs and discharge them to around 4 amps within 15ms. So, that part satisfies me. I'm just not sure how to incorporate a power switch to the microcontroller without messing up the caps performance.

    Please see attached image.
  2. mik3

    Senior Member

    Feb 4, 2008
    If the charging voltage is 20V, use a 15V zener in series with a 220R resistor.
  3. iONic

    AAC Fanatic!

    Nov 16, 2007
    From what I've understood most modern micro controllers don't consume much power at all, some even have sleep modes and the power consumption is in the uA.
  4. SgtWookie


    Jul 17, 2007
    Yep - 10uA or so to have the uC take a nap, or 20mA to run the SSR's diode to save that 10uA.